Assembly Guide

Step-by-step hardware assembly instructions for the 3we robot platform.

	Basic SKU	Standard SKU
Time	2-3 hours	4-5 hours
Difficulty	Intermediate (soldering required)	Intermediate-Advanced
Cost	~¥680 / $95	~¥2,200 / $300
Prerequisites	Basic soldering, multimeter use	+ Linux CLI, micro-SD flashing

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Safety Warnings

1. LiPo batteries can cause fire if short-circuited or punctured. Never leave charging unattended.
2. Soldering iron temperatures exceed 300°C. Use a silicone mat and keep the tip clean.
3. E-stop wiring is safety-critical. Double-check before first power-on (Step 7).
4. Motors under load can draw 2A+ per channel. Do not exceed DRV8833 ratings (1.5A continuous per channel).
5. Disconnect the battery XT30 connector before any wiring changes.

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Tools Required

• Phillips screwdriver (PH1, PH2)
• Hex key set (M2, M2.5, M3)
• Soldering iron (for motor wires)
• Wire strippers
• Multimeter
• 3D printer (for custom brackets, optional)

Parts Checklist

Before starting, verify you have all components from the Bill of Materials.

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Step 1: Chassis Preparation

1. Inspect the aluminum chassis for burrs or bent edges
2. Install M2.5 brass standoffs (x4) for PCB mounting
3. Install M3 threaded inserts (x4) for payload mounting plate
4. Verify all mounting holes align with the 20mm grid pattern

Step 2: Motor Installation

Motor orientation is critical for correct mecanum movement:

        FRONT
   [FL ╲]     [╱ FR]
   ┌──────────────┐
   │              │
   │   CHASSIS    │
   │              │
   └──────────────┘
   [╱ RL]     [RR ╲]
        REAR

1. Mount motors in their brackets using M2 screws
2. Secure brackets to chassis corners with M3x8mm bolts
3. Route motor wires through internal cable channels
4. Solder JST-PH connectors to motor leads:
   • Red — Motor+ (positive terminal)
   • Black — Motor- (negative terminal)
   • Green — Encoder A
   • White — Encoder B
   • Red (thin) — Encoder VCC (3.3V)
   • Black (thin) — Encoder GND

Step 3: Wheel Mounting

Critical: Mecanum roller direction matters!

• Front-Left & Rear-Right: Left-handed rollers (╲ pattern when viewed from front)
• Front-Right & Rear-Left: Right-handed rollers (╱ pattern when viewed from front)

1. Press wheel onto motor D-shaft
2. Secure with M3 set screw (use threadlocker)
3. Verify wheel spins freely without wobble
4. Check ground clearance >= 25mm

Step 4: PCB / Electronics Installation

1. Place ESP32-S3 and motor drivers on standoffs
2. Secure with M2.5 nylon screws (to avoid shorts)
3. Connect motor cables to DRV8833 (match FL/FR/RL/RR labels)
4. Connect encoder cables to ESP32-S3 GPIO headers
5. Verify no cables are pinched or strained

Step 5: Sensor Installation

IMU (BNO055)

1. Mount at geometric center of chassis, as flat as possible
2. Secure with M2 screws or double-sided tape (vibration-resistant)
3. Connect I2C cable (4-pin: VCC, GND, SDA, SCL)
4. Note mounting orientation (arrow on PCB = forward/X-axis)

LiDAR (LD06) - Standard SKU

1. Mount on top using the provided bracket
2. Position centrally with clear 360-degree line of sight
3. Connect via USB-UART adapter to Pi 5

Camera - Standard SKU

1. Mount on front-facing bracket
2. Connect via USB3 to Pi 5
3. Ensure 160-degree field of view is unobstructed

Step 6: Battery Installation

1. Mount 3S LiPo battery centrally (lowest possible for CG)
2. Verify BMS LED indicates correct voltage
3. Secure with velcro strap or 3D-printed retention clip
4. Route XT30 cable to power distribution
5. DO NOT connect yet — wait until final inspection

Step 7: Emergency Stop Wiring

This is a safety-critical step. Double-check all connections.

E-Stop Button (NC contact)
    Pin 1 ──→ Safety Relay Coil (+)
    Pin 2 ──→ Safety Relay Coil (-)
                    │
Safety Relay NO Contact:
    COM ──→ Battery VBAT
    NO  ──→ DRV8833 Motor Power Input

1. Mount E-stop button on chassis top (accessible, labeled)
2. Wire NC contact to safety relay coil terminals
3. Wire relay NO contact in series with motor power line
4. Verify: When button is UP (normal), relay energized, motors powered
5. Verify: When button is DOWN (pressed), relay de-energized, motors cut

Step 8: Wiring Summary

From	To	Interface
Pi 5	ESP32-S3	USB-C (micro-ROS)
ESP32-S3	DRV8833 x2	GPIO (PWM + DIR)
DRV8833	JGA25-370 Motors	Direct wire
Pi 5	LD06 LiDAR	USB-UART
Pi 5	Camera	USB3
ESP32-S3	BNO055	I2C
E-Stop	Safety Relay	NC contact
Safety Relay	Motor power	Inline

Step 9: Final Inspection

Before powering on for the first time:

• All motor wires connected and secure
• Battery polarity correct
• E-stop button wired correctly (NC)
• No loose wires or exposed conductors
• No cables interfering with wheel rotation
• All screws tightened
• IMU mounted flat and centered
• LiDAR has clear 360-degree line of sight

First Power-On Procedure

1. Press E-stop button DOWN (motors locked out)
2. Connect battery XT30 connector
3. Verify power LED illuminates
4. Check ESP32 serial output for boot messages
5. Verify all sensor readings are reasonable
6. Release E-stop button (twist to reset)
7. Test motor movement with low speed commands

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Troubleshooting

Symptom	Likely Cause	Fix
No power LED	Battery disconnected or BMS tripped	Check XT30, verify cell voltage
Motors don’t spin	E-stop active or relay wiring	Check relay state, verify NC wiring
Wrong movement direction	Motor wires swapped	Swap IN1/IN2 wires for affected motor
Robot curves when going straight	Wheel type swapped	Verify roller direction (Step 3)
IMU drift	Bad mounting or calibration	Re-mount flat, run calibration routine

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After Assembly

Once powered on and confirmed working:

1. Flash firmware — See Firmware Guide for ESP-IDF build and flash
2. Basic SKU: Use WiFi teleop for initial control
3. Standard SKU: Install ROS2 on Pi 5, then follow Getting Started